Stocking at
high density may change the feeding habits of fish
species, diverting them to food that is more available,
usually detritus (Schroeder 1980). This leads to
direct competition for food among fish species and a
loss of the advantage of polyculture (Hepher,
Milstein, Leventer & Teltsch 1989). In our experiments,
the fish stocking density varied between 0.5
and 2.5 fishm±2 if one calculates the stocking density
as number of fish per trench + field' area, as is widely
done. However, if one calculates the stocking density
as number of fish per trench area, one obtains a
stocking density varying between 3.33 and 16.5 fish
m±2. It can be argued that the latter should be used
for fish culture in rice fields as the field aquatic
conditions are far from optimal for fish culture
during a substantial part of the rice cropping season.